Introduction to the Issue on Automatic Assessment of Health Disorders Based on Voice, Speech, and Language Processing

Approximately one-fifth of the world's population suffer or have suffered from voice and speech production disorders due to diseases or some other dysfunction. Thus, there is a clear need for objective ways to evaluate the quality of voice and speech as well as its link to vocal fold activity, to evaluate the complex interaction between the larynx and voluntary movements of the articulators (i.e., lips, teeth, tongue, velum, jaw, etc), or to evaluate disfluencies at the language level. The underlying assumption is that deviations from patterns that might be considered normal can be correlated with many different symptoms and psychophysical situations. However, despite a large effort in this field in the last few years, useful services are still far fewer than those in other areas of speech technology (text-to-speech synthesis, speech recognition, speaker recognition and verification, etc.) and, as a result, many results have not been transferred to clinical settings.

In addition, the processing of the speech signal not only lets evaluate voice disorders, but also opens the door to contribute to the examination of other health disorders. The current state of the art is now opening the possibility of early detection, monitoring and evaluation of certain pathologies whose etiology is not directly related to the speech apparatus, such as Alzheimer's, Parkinson, other Parkinsonisms (amyotrophic lateral sclerosis, Huntington's disease…), dementia, autism, attention deficit hyperactivity disorder, depression, and obstructive sleep apnea, among others, which manifest certain alterations in speech at phonation, articulation, prosodic, or even linguistic levels.

The maturity of current speech technologies and earlier results reported in the specific field of this issue demonstrate the potential of addressing these challenges to provide new tools for clinicians. However, the application of speech technologies to the assessment of voice and health disorders is not restricted to the medical area alone, as it may also be of interest in forensic applications, the assessment of voice quality for voice professionals such as singers, the evaluation of stress and fatigue, the evaluation of surgical as well as pharmacological treatments and rehabilitation, etc.